In recent years, various electric home appliances, including consumer game machines, have highly sophisticated functions, and many appliances are adapted to expansion of the function thereof by connecting a peripheral device to the main bodies thereof. For such a product, it may be desirable to determine whether or not a peripheral device is an authentic product (a genuine product), in order to avoid any expected trouble which could be caused by the user by connecting by mistake a product of a different brand to the main body.
In view of the above, there is an idea in which an authentication process generally used for computers is carried out between the main body of an electric home appliance and a peripheral device to determine whether or not the peripheral device is an authentic product. For example, Patent Document 1 discloses an example of an authentication process of a typical challenge-response type. As an example algorithm for realizing such an authentication process, there is available a common key encryption algorithm according to which both of an authentication requesting device, such as the main body of an electric home appliance and so forth, which requests authentication and an authentication target device, such as a peripheral device, to be a target of an authentication process possess a common encryption key (a common key).    Patent Document 1: Japanese Patent Laid-open Publication No. Hei 11-163853